The present invention relates to processes of making biaxially textured substrates that include rolling steps, and more particularly to such processes wherein shear force is introduced into the process in order to avoid the need for annealing steps to produce a sharp biaxial texture, and other attributes such as fine grain sizes and elongated grains.
High critical current density conductors fabricated by epitaxial deposition of high temperature superconductors on biaxially textured substrates is considered to be a viable route towards realizing low cost, high performance superconducting wires for a variety of applications. A well-formed cube texturexe2x80x94a biaxially textured face centered cubic (FCC) crystalline structurexe2x80x94is first developed in a metal (pure metal or metal alloy) substrate (template), followed by epitaxial deposition of intermediate oxide buffer layers and superconductors.
The following U.S. Patents are expressly referenced, and the entire disclosure of each listed patent is expressly incorporated herein by reference:
U.S. Pat. No. 6,486,100 issued on Nov. 26, 2002 to Goyal, et al., entitled Method for Preparing Preferentially Oriented, High Temperature Superconductors using Solution Reagents.
U.S. Pat. No. 6,468,591 issued on Oct. 22, 2002 to Goyal, et al., entitled Method For Making MgO Buffer Layers on Rolled Nickel or Copper as Superconductor Substrates.
U.S. Pat. No. 6,451,450 issued on Sep. 17, 2002 to Feenstra, et al., entitled Method of Depositing a Protective Layer Over a Biaxially Textured Alloy Substrate and Composition Therefrom.
U.S. Pat. No. 6,447,714 issued on Sep. 10, 2002 to Goyal, et al., entitled Method for Forming Biaxially Textured Articles by Powder Metallurgy.
U.S. Pat. No. 6,440,211 issued on Aug. 27, 2002 to Beach, et al., entitled Method of Depositing Buffer Layers on Biaxially Textured Metal Substrates.
U.S. Pat. No. 6,399,154 issued on Jun. 4, 2002 to Feenstra, et al., entitled Laminate Article.
U.S. Pat. No. 6,375,768 issued on Apr. 23, 2002 to Goyal, entitled Method for Making Biaxially Textured Articles by Plastic Deformation.
U.S. Pat. No. 6,331,199 issued on Dec. 18, 2001 to Goyal, et al., entitled Biaxially Textured Articles formed by Powder Metallurgy.
U.S. Pat. No. 6,270,908 issued on Aug. 7, 2001 to Feenstra, et al., entitled Rare Earth Zirconium Oxide Buffer Layers on Metal Substrates.
U.S. Pat. No. 6,261,704 issued on Jul. 17, 2001 to Goyal, et al., entitled MgO Buffer Layers on Rolled Nickel or Copper as Superconductor Substrates.
U.S. Pat. No. 6,256,521 issued on Jul. 3, 2001 to Goyal, et al., entitled Preferentially Oriented, High Temperature Superconductors by Seeding and a Method for their Preparation.
U.S. Pat. No. 6,235,402 issued on May 22, 2001 to Beach, et al., entitled Buffer Layers on Biaxially Textured Metal Substrates.
U.S. Pat. No. 6,180,570 issued on Jan. 30, 2001 to Goyal, entitled Biaxially Textured Articles formed by Plastic Deformation.
U.S. Pat. No. 6,159,610 issued on Dec. 12, 2000 to Goyal, et al., entitled Buffer Layers on Metal Surfaces having Biaxial Texture as Superconductor Substrates.
U.S. Pat. No. 6,156,376 issued. on Dec. 5, 2000 to Goyal, et al., entitled Buffer Layers on Metal Surfaces having Biaxial Texture as Superconductor Substrates.
U.S. Pat. No. 6,150,034 issued on Nov. 21, 2000 to Goyal, et al., entitled Buffer Layers on Rolled Nickel or Copper as Superconductor Substrates.
U.S. Pat. No. 6,114,287 issued on Sep. 5, 2000 to Goyal, et al., entitled Method of Deforming a Biaxially Textured Buffer Layer on a Textured Metallic Substrate and Articles Therefrom.
U.S. Pat. No. 6,106,615 issued on Aug. 22, 2000 to Goyal, et al., entitled Method of Forming Biaxially Textured Alloy Substrates and Devices Thereon.
U.S. Pat. No. 6,077,344 issued on Jun. 20, 2000 to Beach, et al., entitled Sol-Gel Deposition of Buffer Layers on Biaxially Textured Metal Substances.
U.S. Pat. No. 5,968,877 issued on Oct. 19, 1999 to Budai, et al., entitled High Tc YBCO Superconductor Deposited on Biaxially Textured Ni Substrate.
U.S. Pat. No. 5,964,966 issued on Oct. 12, 1999 to Goyal, et al., entitled Method of Forming Biaxially Textured Alloy Substrates and Devices Thereon.
U.S. Pat. No. 5,958,599 issued on Sep. 28, 1999 to Goyal, et al., entitled Structures Having Enhanced Biaxial Texture.
U.S. Pat. No. 5,898,020 issued on Apr. 27, 1999 to Goyal, et al., entitled Structures Having Enhanced Biaxial Texture and Method of Fabricating Same.
U.S. Pat. No. 5,846,912 issued on Dec. 8, 1998 to Goyal, et al., entitled Method for Preparation of Textured YBa2Cu30x Superconductor.
U.S. Pat. No. 5,741,377 issued on Apr. 21, 1998 to Goyal, et al., entitled Structures Having Enhanced Biaxial Texture and Method of Fabricating Same.
U.S. Pat. No. 5,739,086 issued on Apr. 14, 1998 to Goyal, et al., entitled Structures Having Enhanced Biaxial Texture and Method of Fabricating Same.
U.S. patent application Ser. No. 09/406,190 filed on Sep. 27, 1999 by Norton, et al., entitled Buffer Architecture for Biaxially Textured Structures and Method of Fabricating Same.
In the above-taught processes of making biaxially textured substrates, typically a cube texture is formed by rolling and subsequently annealing a metallic preform, usually a metal strip. The as-rolled metal or alloy strip has a rolling texture, which is a complex mixed texture. Annealing of the metal strip is required to form a recrystallization texture, which for FCC metals is the cube texture. High annealing temperatures are generally required in order to form the desired completely cubic texture. Moreover, the resulting grain sizes are also large; the dimensions thereof often approach the thickness of the thin strip. For example, a 50 xcexcm thick substrate, upon complete annealing may often result in a substrate with an average grain size of 50 xcexcm. Furthermore, the grains in a cube-textured strip are generally equiaxed, which is typical of the recrystallization process. A fully annealed, cube textured strip is generally mechanically much softer and weaker compared to the as-rolled strip.
For some applications, it is essential that a fully developed cube texture be formed. For many FCC metals and alloys however, this may require a very high annealing temperature. In some cases upon annealing at high temperatures results in secondary recrystallization of the material and even the previously formed cube texture at lower temperatures is destroyed.
There may be some fundamental limitations towards the fabrication of high-Jc conductors on such templates. One such limitation may be caused by large grain sizes in the substrates with respect to finite width of the substrates, a phenomenon known as percolative pinch-off. The number of grains that exist across the width of a substrate tape is somewhat proportional to the ability of epitaxial superconductors to carry current (Jc), to a point.
Reductions in Jc due to the finite width of the substrate become a less significant negative factor for substrates having a width of at least 100 grains. Hence, for substrates that are at least 0.5 cm (100 grains) wide and have a typical average grain size of no more than 50 xcexcm, the percolative pinch-off of Jc due to a large grain size in the substrate and a finite width of the substrate is less of an issue.
However, for many large-scale applications of superconducting materials, substrate widths of 0.4 cm and even less are required. In these cases, the percolative pinch-off of Jc due to a large grain size in the substrate and a finite width of the substrate is a significant issue.
Accordingly, objects of the present invention include the provision of new methods of making biaxially textured substrates wherein post-rolling heating steps can be reduced or eliminated. The invention provides a method of making substrates with fine grain sizes and/or elongated grains. The invention also provides a method of making textured substrates that are harder and/or stronger than annealed substrates. The invention provides a method of making a biaxially textured substrate with a new kind of biaxial texture. Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a biaxially textured article that includes a directionally rolled, biaxially textured metallic substrate having an as-rolled, rotated cube texture wherein a (100) cube face thereof is parallel to a surface of said article, and wherein a [100] direction thereof is at an angle of at least 10xc2x0 relative to a rolling direction thereof, the substrate having thereon at least one epitaxial layer of another material.
In accordance with another aspect of the present invention, a method of preparing a biaxially textured article includes the steps of: rolling a metal preform while applying shear force thereto to form as-rolled biaxially textured substrate having an a rotated cube texture wherein a (100) cube face thereof is parallel to a surface of said substrate, and wherein a [100] direction thereof is at an angle of at least 10xc2x0 relative to a rolling direction; and depositing onto the surface of the biaxially textured substrate at least one epitaxial layer of another material to form a biaxially textured article.